textproduct: Quad Cities

KEY MESSAGES

- Another clipper system will graze our northeast tonight into early Thursday morning, with a 20% to 40% chance of light rain over northwest Illinois. If temperatures can reach the freezing mark, some freezing rain can't be ruled out.

- Temperatures will gradually increase today through the end of the week, warming to well above normal by the weekend.

SHORT TERM /THROUGH TONIGHT/

Issued at 245 AM CDT Wed Mar 18 2026

The ongoing clipper system is just beginning to wind down as the associated mid-level shortwave and attendant large-scale forcing continues to shift off to the southeast. Up to this point, the sub- cloud layer of dry air has really helped to limit snow accumulations, with amounts less than one inch being reported. Eventually, all remaining precipitation will end later this morning (most likely around sunrise, if not sooner), leading to dry conditions through at least this afternoon. A large upper-level high pressure system will take hold over the southwestern CONUS today, leading to a large longwave ridge to develop over the western half of the US. This will keep our weather conditions mostly dry for the next several days.

The only exception to this will be yet another clipper system that will ride the leeward side of the ridge tonight into early Thursday morning, resulting in a glancing chance of light precipitation (20- 40% chance) across northwest Illinois. Both the 18.00z HREF and REFS ensembles strongly suggest precip types to be largely rain, although there is a low chance (less than 20%) of freezing rain if temperatures can dip to the freezing mark. It appears likely that should freezing rain develop, it will be a fleeting window, likely due to latent heat release and a lack of north to northeast flow that could help overcome these effects. Impacts from this event should remain minimal.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 245 AM CDT Wed Mar 18 2026

The upper-level pattern won't change much for Thursday through Saturday as the aforementioned upper-level ridging remains in control over the western US. Dry conditions should prevail for this period, with the primary focus being on our temperatures as a pronounced warm-up is expected. NBM suggests highs on Thursday to warm to the lower 50s/lower 60s up to the 70s area-wide by Saturday. Both the GEFS and ECWMF ensemble means suggest 850 temperatures to warm to around the mid/upper teens Celsius by Saturday, although differing on when the peak of the thermal ridge moves through. The ECMWF EFI values for Saturday's high temperatures are reaching 0.7 to 0.9 across our forecast area, a strong signal for anomalously warm temperatures.

Sunday through Tuesday: the synoptic pattern changes to a more zonal flow aloft by Sunday, which would be more supportive of any waves moving through the area. Indeed, the global models/LREF ensemble suggests a cold front to sweep through our area on Sunday, although there are significant differences on both the timing of the boundary and if any precipitation will form along it. Both the NBM and LREF ensemble have chances of any measurable rainfall along the front to be less than 20%, so low chances at this time. The bigger impact from the front will be on our temperatures as they should gradually cool into Monday, when temperatures are likely to be closer to average for this time of the year (middle/upper 40s for highs and upper 20s/lower 30s for lows). Other than the low chances of precip along the front, no other systems are expected for this period, so dry conditions should continue.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 537 AM CDT Wed Mar 18 2026

An area of MVFR stratus to impact DBQ through 14z today. Otherwise VFR conditions to prevail through the entire period at all TAF sites expect DBQ. Another weak shortwave will drop south out of the upper Midwest after 00z.19 with increasing clouds and rain chances over northeast IA and northern IL. MVFR conditions will be possible at DBQ late in the period and just beyond.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.